The present invention concerns a method of detecting a minute defect occurred on a test specimen and a device therefor, and more particularly relates to a defect inspection method suitable for detecting a minute defect occurred on a semiconductor wafer with a fine pattern formed on its surface and a device therefor.
A semiconductor wafer is made more and more multi-layered in structure as the shape of a pattern to be formed on the wafer is more and more refined with high-integration of a circuit, and the number of producing steps thereof is being steadily increased. In order to stably produce a highly reliable high-integrated circuit by surely forming the fine pattern on the wafer, it becomes important to confirm that the fine pattern is surely formed and a defect such as a foreign matter or the like does not occur by inspecting the wafer on which the pattern is formed.
As a means for inspecting the wafer with the pattern formed thereon, there exist, for example, a pattern inspection device of light-field-based optical system (a light-field pattern inspection device), a defect inspection device of dark-field-based optical system (a dark-field defect inspection device) and others.
Although the applications of the light-field pattern inspection device and the dark-field inspection device are different from each other in general, the dark-field defect inspection device has such a feature that throughput of inspection is higher than that of the light-field pattern inspection device.
In such a dark-field defect inspection device as mentioned above, how a more minute defect is to be detected at a higher speed without being affected by light scattered from the pattern formed on the wafer is one of problems.
As a means for solving this problem, in Japanese Patent Application Laid-Open No. 2000-105203 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2001-512237 (Patent Document 2), there is a description that a wafer is obliquely irradiated with linear illumination light which is finely squeezed in one direction and light which has been scattered from a surface of the wafer with the linear illumination light is detected by a detection system above the wafer and detection systems disposed on its both sides while continuously moving the wafer in a direction orthogonal to a longitudinal direction of the illumination light, thereby detecting a defect on the wafer by using respective detection signals.
In addition, in Japanese Patent Application Laid-Open No. 2010-256340 (Patent Document 3), there is a description that a TDI (Time Delay Integration) sensor is used in a detection system and it is configured to asynchronously control a line rate of the TDI sensor and a stage scan speed to illuminate an object to be inspected with finely squeezed linear light so as to make only an arbitrary pixel line of the TDL sensor receive scattered light from the inspected object such that an aspect ratio of the size of a detection pixel can be controlled with a speed ratio of the line rate of the TDI sensor to the stage scan speed, thereby making inspection possible at a scan speed higher than the line rate of the TDI sensor.
Further, in Japanese Patent Application Laid-Open No. 2010-190722 (Patent Document 4), there is a description that a wafer is obliquely irradiated with linear illumination light which is finely squeezed in one direction, light which has been scattered upward from a surface of the wafer with the linear illumination light is collected while continuously moving the wafer in a direction orthogonal to a longitudinal direction of the linear illumination light and is branched in accordance with a state of polarization, light transmitted through a spatial filter is detected by filtering diffracted light and scattered light from a normal pattern by the arrayed spatial filter, thereby detecting a defect independently of polarization characteristics of scattered light from the defect.